1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Xen SMP support
4 *
5 * This file implements the Xen versions of smp_ops. SMP under Xen is
6 * very straightforward. Bringing a CPU up is simply a matter of
7 * loading its initial context and setting it running.
8 *
9 * IPIs are handled through the Xen event mechanism.
10 *
11 * Because virtual CPUs can be scheduled onto any real CPU, there's no
12 * useful topology information for the kernel to make use of. As a
13 * result, all CPUs are treated as if they're single-core and
14 * single-threaded.
15 */
16 #include <linux/sched.h>
17 #include <linux/sched/task_stack.h>
18 #include <linux/err.h>
19 #include <linux/slab.h>
20 #include <linux/smp.h>
21 #include <linux/irq_work.h>
22 #include <linux/tick.h>
23 #include <linux/nmi.h>
24 #include <linux/cpuhotplug.h>
25 #include <linux/stackprotector.h>
26 #include <linux/pgtable.h>
27
28 #include <asm/paravirt.h>
29 #include <asm/idtentry.h>
30 #include <asm/desc.h>
31 #include <asm/cpu.h>
32 #include <asm/apic.h>
33 #include <asm/io_apic.h>
34
35 #include <xen/interface/xen.h>
36 #include <xen/interface/vcpu.h>
37 #include <xen/interface/xenpmu.h>
38
39 #include <asm/spec-ctrl.h>
40 #include <asm/xen/interface.h>
41 #include <asm/xen/hypercall.h>
42
43 #include <xen/xen.h>
44 #include <xen/page.h>
45 #include <xen/events.h>
46
47 #include <xen/hvc-console.h>
48 #include "xen-ops.h"
49
50 cpumask_var_t xen_cpu_initialized_map;
51
52 static DEFINE_PER_CPU(struct xen_common_irq, xen_irq_work) = { .irq = -1 };
53 static DEFINE_PER_CPU(struct xen_common_irq, xen_pmu_irq) = { .irq = -1 };
54
55 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
56
cpu_bringup(void)57 static void cpu_bringup(void)
58 {
59 int cpu;
60
61 cr4_init();
62 cpuhp_ap_sync_alive();
63 cpu_init();
64 fpu__init_cpu();
65 touch_softlockup_watchdog();
66
67 /* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
68 if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
69 xen_enable_sysenter();
70 xen_enable_syscall();
71 }
72 cpu = smp_processor_id();
73 smp_store_cpu_info(cpu);
74 set_cpu_sibling_map(cpu);
75
76 speculative_store_bypass_ht_init();
77
78 xen_setup_cpu_clockevents();
79
80 notify_cpu_starting(cpu);
81
82 set_cpu_online(cpu, true);
83
84 smp_mb();
85
86 /* We can take interrupts now: we're officially "up". */
87 local_irq_enable();
88 }
89
cpu_bringup_and_idle(void)90 asmlinkage __visible void cpu_bringup_and_idle(void)
91 {
92 cpu_bringup();
93 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
94 }
95
xen_smp_intr_free_pv(unsigned int cpu)96 void xen_smp_intr_free_pv(unsigned int cpu)
97 {
98 kfree(per_cpu(xen_irq_work, cpu).name);
99 per_cpu(xen_irq_work, cpu).name = NULL;
100 if (per_cpu(xen_irq_work, cpu).irq >= 0) {
101 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu).irq, NULL);
102 per_cpu(xen_irq_work, cpu).irq = -1;
103 }
104
105 kfree(per_cpu(xen_pmu_irq, cpu).name);
106 per_cpu(xen_pmu_irq, cpu).name = NULL;
107 if (per_cpu(xen_pmu_irq, cpu).irq >= 0) {
108 unbind_from_irqhandler(per_cpu(xen_pmu_irq, cpu).irq, NULL);
109 per_cpu(xen_pmu_irq, cpu).irq = -1;
110 }
111 }
112
xen_smp_intr_init_pv(unsigned int cpu)113 int xen_smp_intr_init_pv(unsigned int cpu)
114 {
115 int rc;
116 char *callfunc_name, *pmu_name;
117
118 callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
119 per_cpu(xen_irq_work, cpu).name = callfunc_name;
120 rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
121 cpu,
122 xen_irq_work_interrupt,
123 IRQF_PERCPU|IRQF_NOBALANCING,
124 callfunc_name,
125 NULL);
126 if (rc < 0)
127 goto fail;
128 per_cpu(xen_irq_work, cpu).irq = rc;
129
130 if (is_xen_pmu) {
131 pmu_name = kasprintf(GFP_KERNEL, "pmu%d", cpu);
132 per_cpu(xen_pmu_irq, cpu).name = pmu_name;
133 rc = bind_virq_to_irqhandler(VIRQ_XENPMU, cpu,
134 xen_pmu_irq_handler,
135 IRQF_PERCPU|IRQF_NOBALANCING,
136 pmu_name, NULL);
137 if (rc < 0)
138 goto fail;
139 per_cpu(xen_pmu_irq, cpu).irq = rc;
140 }
141
142 return 0;
143
144 fail:
145 xen_smp_intr_free_pv(cpu);
146 return rc;
147 }
148
xen_pv_smp_config(void)149 static void __init xen_pv_smp_config(void)
150 {
151 u32 apicid = 0;
152 int i;
153
154 topology_register_boot_apic(apicid);
155
156 for (i = 0; i < nr_cpu_ids; i++)
157 topology_register_apic(apicid++, CPU_ACPIID_INVALID, true);
158
159 /* Pretend to be a proper enumerated system */
160 smp_found_config = 1;
161 }
162
xen_pv_smp_prepare_boot_cpu(void)163 static void __init xen_pv_smp_prepare_boot_cpu(void)
164 {
165 BUG_ON(smp_processor_id() != 0);
166 native_smp_prepare_boot_cpu();
167
168 if (!xen_feature(XENFEAT_writable_page_tables))
169 /* We've switched to the "real" per-cpu gdt, so make
170 * sure the old memory can be recycled. */
171 make_lowmem_page_readwrite(xen_initial_gdt);
172
173 xen_setup_vcpu_info_placement();
174
175 /*
176 * The alternative logic (which patches the unlock/lock) runs before
177 * the smp bootup up code is activated. Hence we need to set this up
178 * the core kernel is being patched. Otherwise we will have only
179 * modules patched but not core code.
180 */
181 xen_init_spinlocks();
182 }
183
xen_pv_smp_prepare_cpus(unsigned int max_cpus)184 static void __init xen_pv_smp_prepare_cpus(unsigned int max_cpus)
185 {
186 unsigned cpu;
187
188 if (ioapic_is_disabled) {
189 char *m = (max_cpus == 0) ?
190 "The nosmp parameter is incompatible with Xen; " \
191 "use Xen dom0_max_vcpus=1 parameter" :
192 "The noapic parameter is incompatible with Xen";
193
194 xen_raw_printk(m);
195 panic(m);
196 }
197 xen_init_lock_cpu(0);
198
199 smp_prepare_cpus_common();
200
201 speculative_store_bypass_ht_init();
202
203 xen_pmu_init(0);
204
205 if (xen_smp_intr_init(0) || xen_smp_intr_init_pv(0))
206 BUG();
207
208 if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
209 panic("could not allocate xen_cpu_initialized_map\n");
210
211 cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
212
213 /* Restrict the possible_map according to max_cpus. */
214 while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
215 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
216 continue;
217 set_cpu_possible(cpu, false);
218 }
219
220 for_each_possible_cpu(cpu)
221 set_cpu_present(cpu, true);
222 }
223
224 static int
cpu_initialize_context(unsigned int cpu,struct task_struct * idle)225 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
226 {
227 struct vcpu_guest_context *ctxt;
228 struct desc_struct *gdt;
229 unsigned long gdt_mfn;
230
231 if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
232 return 0;
233
234 ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
235 if (ctxt == NULL) {
236 cpumask_clear_cpu(cpu, xen_cpu_initialized_map);
237 return -ENOMEM;
238 }
239
240 gdt = get_cpu_gdt_rw(cpu);
241
242 /*
243 * Bring up the CPU in cpu_bringup_and_idle() with the stack
244 * pointing just below where pt_regs would be if it were a normal
245 * kernel entry.
246 */
247 ctxt->user_regs.eip = (unsigned long)asm_cpu_bringup_and_idle;
248 ctxt->flags = VGCF_IN_KERNEL;
249 ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
250 ctxt->user_regs.ds = __USER_DS;
251 ctxt->user_regs.es = __USER_DS;
252 ctxt->user_regs.ss = __KERNEL_DS;
253 ctxt->user_regs.cs = __KERNEL_CS;
254 ctxt->user_regs.esp = (unsigned long)task_pt_regs(idle);
255
256 xen_copy_trap_info(ctxt->trap_ctxt);
257
258 BUG_ON((unsigned long)gdt & ~PAGE_MASK);
259
260 gdt_mfn = arbitrary_virt_to_mfn(gdt);
261 make_lowmem_page_readonly(gdt);
262 make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
263
264 ctxt->gdt_frames[0] = gdt_mfn;
265 ctxt->gdt_ents = GDT_ENTRIES;
266
267 /*
268 * Set SS:SP that Xen will use when entering guest kernel mode
269 * from guest user mode. Subsequent calls to load_sp0() can
270 * change this value.
271 */
272 ctxt->kernel_ss = __KERNEL_DS;
273 ctxt->kernel_sp = task_top_of_stack(idle);
274
275 ctxt->gs_base_kernel = per_cpu_offset(cpu);
276 ctxt->event_callback_eip =
277 (unsigned long)xen_asm_exc_xen_hypervisor_callback;
278 ctxt->failsafe_callback_eip =
279 (unsigned long)xen_failsafe_callback;
280 per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
281
282 ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_gfn(swapper_pg_dir));
283 if (HYPERVISOR_vcpu_op(VCPUOP_initialise, xen_vcpu_nr(cpu), ctxt))
284 BUG();
285
286 kfree(ctxt);
287 return 0;
288 }
289
xen_pv_kick_ap(unsigned int cpu,struct task_struct * idle)290 static int xen_pv_kick_ap(unsigned int cpu, struct task_struct *idle)
291 {
292 int rc;
293
294 rc = common_cpu_up(cpu, idle);
295 if (rc)
296 return rc;
297
298 xen_setup_runstate_info(cpu);
299
300 /* make sure interrupts start blocked */
301 per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
302
303 rc = cpu_initialize_context(cpu, idle);
304 if (rc)
305 return rc;
306
307 xen_pmu_init(cpu);
308 mc_percpu_init(cpu);
309
310 /*
311 * Why is this a BUG? If the hypercall fails then everything can be
312 * rolled back, no?
313 */
314 BUG_ON(HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL));
315
316 return 0;
317 }
318
xen_pv_poll_sync_state(void)319 static void xen_pv_poll_sync_state(void)
320 {
321 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
322 }
323
324 #ifdef CONFIG_HOTPLUG_CPU
xen_pv_cpu_disable(void)325 static int xen_pv_cpu_disable(void)
326 {
327 unsigned int cpu = smp_processor_id();
328 if (cpu == 0)
329 return -EBUSY;
330
331 cpu_disable_common();
332
333 load_cr3(swapper_pg_dir);
334 return 0;
335 }
336
xen_pv_cpu_die(unsigned int cpu)337 static void xen_pv_cpu_die(unsigned int cpu)
338 {
339 while (HYPERVISOR_vcpu_op(VCPUOP_is_up, xen_vcpu_nr(cpu), NULL)) {
340 __set_current_state(TASK_UNINTERRUPTIBLE);
341 schedule_timeout(HZ/10);
342 }
343 }
344
xen_pv_cleanup_dead_cpu(unsigned int cpu)345 static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
346 {
347 xen_smp_intr_free(cpu);
348 xen_uninit_lock_cpu(cpu);
349 xen_teardown_timer(cpu);
350 xen_pmu_finish(cpu);
351 }
352
xen_pv_play_dead(void)353 static void __noreturn xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */
354 {
355 play_dead_common();
356 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL);
357 xen_cpu_bringup_again((unsigned long)task_pt_regs(current));
358 BUG();
359 }
360
361 #else /* !CONFIG_HOTPLUG_CPU */
xen_pv_cpu_disable(void)362 static int xen_pv_cpu_disable(void)
363 {
364 return -ENOSYS;
365 }
366
xen_pv_cpu_die(unsigned int cpu)367 static void xen_pv_cpu_die(unsigned int cpu)
368 {
369 BUG();
370 }
371
xen_pv_cleanup_dead_cpu(unsigned int cpu)372 static void xen_pv_cleanup_dead_cpu(unsigned int cpu)
373 {
374 BUG();
375 }
376
xen_pv_play_dead(void)377 static void __noreturn xen_pv_play_dead(void)
378 {
379 BUG();
380 }
381
382 #endif
stop_self(void * v)383 static void stop_self(void *v)
384 {
385 int cpu = smp_processor_id();
386
387 /* make sure we're not pinning something down */
388 load_cr3(swapper_pg_dir);
389 /* should set up a minimal gdt */
390
391 set_cpu_online(cpu, false);
392
393 HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL);
394 BUG();
395 }
396
xen_pv_stop_other_cpus(int wait)397 static void xen_pv_stop_other_cpus(int wait)
398 {
399 smp_call_function(stop_self, NULL, wait);
400 }
401
xen_irq_work_interrupt(int irq,void * dev_id)402 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
403 {
404 irq_work_run();
405 inc_irq_stat(apic_irq_work_irqs);
406
407 return IRQ_HANDLED;
408 }
409
xen_smp_count_cpus(void)410 void __init xen_smp_count_cpus(void)
411 {
412 unsigned int cpus;
413
414 for (cpus = 0; cpus < nr_cpu_ids; cpus++) {
415 if (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpus, NULL) < 0)
416 break;
417 }
418
419 pr_info("Xen PV: Detected %u vCPUS\n", cpus);
420 if (cpus < nr_cpu_ids)
421 set_nr_cpu_ids(cpus);
422 }
423
424 static const struct smp_ops xen_smp_ops __initconst = {
425 .smp_prepare_boot_cpu = xen_pv_smp_prepare_boot_cpu,
426 .smp_prepare_cpus = xen_pv_smp_prepare_cpus,
427 .smp_cpus_done = xen_smp_cpus_done,
428
429 .kick_ap_alive = xen_pv_kick_ap,
430 .cpu_die = xen_pv_cpu_die,
431 .cleanup_dead_cpu = xen_pv_cleanup_dead_cpu,
432 .poll_sync_state = xen_pv_poll_sync_state,
433 .cpu_disable = xen_pv_cpu_disable,
434 .play_dead = xen_pv_play_dead,
435
436 .stop_other_cpus = xen_pv_stop_other_cpus,
437 .smp_send_reschedule = xen_smp_send_reschedule,
438
439 .send_call_func_ipi = xen_smp_send_call_function_ipi,
440 .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
441 };
442
xen_smp_init(void)443 void __init xen_smp_init(void)
444 {
445 smp_ops = xen_smp_ops;
446
447 /* Avoid searching for BIOS MP tables */
448 x86_init.mpparse.find_mptable = x86_init_noop;
449 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop;
450
451 /* XEN/PV Dom0 has halfways sane topology information via CPUID/MADT */
452 if (xen_initial_domain())
453 x86_init.mpparse.parse_smp_cfg = x86_init_noop;
454 else
455 x86_init.mpparse.parse_smp_cfg = xen_pv_smp_config;
456 }
457